The invention relates to a clamping device for fixing plastic molded parts during welding, comprising a flange-like fastening part for fastening on a plastics welding device, the fastening part having at least one first annular recess for receiving a clamping element and the fastening part having at least one second recess for receiving spring elements acting radially on the clamping element.
In pipeline construction, plastic molded parts, such as pipe bends and pipe branches for example, are being increasingly used and are welded to one another on the construction site. The plastic molded pipe parts are fixed in axial alignment with one another in a special welding device and worked at right angles and in a planar manner. The pipe ends are heated up and pressed axially together. During the welding operation, the plastic molded pipe parts are firmly held on the welding device by clamping systems.
U.S. Pat. No. 5,241,157 discloses a device for welding the end faces of plastic parts, which discloses, inter alia, two generically determinative clamping devices. One clamping device is fixed and the second clamping device is axially displaceable in their arrangement in the welding device. The clamping devices take the form of semicircular components which have a relatively large width in the axial direction in comparison with the pipe diameter. The large width is necessary to distribute the clamping force uniformly over the circumference of the molded pipe parts to be welded to one another and thus hold the pipes well in the desired position during the welding operation. It is not described how the clamping force is produced. To make good fixing possible, even in confined spaces and with fittings and molded pipe parts becoming increasingly smaller, novel fixing devices are desired.
It is an object of the invention to provide a clamping element for fixing plastic molded parts during welding, achieving fixing which is as secure as possible and saves as much space as possible.
The foregoing object is achieved by a clamping device for fixing plastic molded parts during welding comprising a flange-like fastening part for fastening on a plastics welding device, the fastening part having at least one first annular recess for receiving a clamping element and the fastening part having at least one second recess for receiving spring elements acting radially on the clamping element, and the clamping element having at least one projection on an inner surface which is arranged opposite the outer surface of the plastic molded part.
It is advantageous that the plastic molded pipe part is firmly held in the welding device securely and as far as possible without damage during welding. This is achieved by the inner surface of the annular clamping element being arranged in an annular and segmental manner, in such a way that the projection encloses the plastic molded part with a uniformly distributed clamping force during the welding operation. This is also achieved by the projection having side surfaces and a clamping surface, the clamping surface being arranged in a concentric and segmentally extending manner with respect to the annular inner surface.
It is also advantageous that the plastic molded pipe part is prevented from creeping out of the welding device during welding. This is achieved by the projections being arranged such that they extend parallel to one another. This is also achieved by the projections being arranged such that they are spaced one behind the other in the axial direction of the plastic parts to be welded.
It is also advantageous that the clamping operation leaves the least possible visible traces behind on the plastic molded pipe part. This is achieved by the projections having a height of 0.1 to 0.3 mm above the inner surface of the clamping element.
It is also advantageous that a highest possible clamping force acts on the plastic molded pipe parts during welding. This is achieved by the clamping surface being arranged at right angles with respect to the side surfaces and adjoining the side surfaces of the projection with sharp edges. This is also achieved by the clamping surface of the projection having a width B of less than 20% of the width of the inner surface of the clamping element.
It is also advantageous that relatively short molded pipe parts can also be reliably welded to one another. This is achieved by the clamping elements being arranged at a distance of less than 25 mm from the welding point of the plastic molded parts to be welded.
It is also advantageous that the plastic molded pipe parts can be introduced easily into the welding device and that the welding device can be put together and operated easily. This is achieved by two fastening parts and two clamping elements being respectively arranged in the plastics welding device for each of the plastic parts to be welded to one another on opposite sides of the welding point as semicircular workpieces matching one another.